The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
As the dissatisfaction of consumers is recently increased due to a difference between certified fuel efficiency and actual fuel efficiency when traveling on the road, an improvement of the actual fuel efficiency is increasingly important. Accordingly, technology for improving actual fuel efficiency when traveling on the road by using driving condition of a driver, surrounding traffic, road information, etc., as well as technology for controlling vehicle systems, has been researched and developed in vehicle industry.
We have discovered that a technique of searching and guiding an economic driving route using IT and traffic information, a technique of guiding driving at high fuel efficiency by memorizing road gradient information and previous traveling patterns, a technique of controlling charge/discharge of a battery according to the SOC (state of charge) level thereof by predicting and determining road gradient and traffic information, and a technique of selectively controlling a traveling mode such that fuel consumption is reduced based on a destination route and traffic information by means of map information DB, are areas to be developed.
One technique for improving the fuel efficiency is an SSC (Start-Stop Coasting) technique. FIGS. 1A and 1B are diagrams for explaining SSC. Referring to FIGS. 1A and 1B, SSC is a technique of cutting off fuel supply to an engine (fuel cut) and cutting off power transfer to a transmission (clutch off) during coasting (see FIG. 1A). We have discovered that the mileage of a vehicle to which the SSC is applied is increased compared to that of the conventional vehicle since engine drag torque is cut off (see FIG. 1B).
In the SCC of the related art, the gear when the SCC is released (when restart is performed) is set according to a pre-stored gear map. The pre-stored gear map is mapped so as to select the gear according to a vehicle speed or the like, regardless of a road gradient. We have discovered that, for this reason, gear shifting may be additionally required according to the road gradient after the SCC is released. In addition, drivability of the vehicle may be deteriorated due to the additional gear shifting according to the road gradient.